Aikido has been stress tested. I'm re-reading my book on Aikido Masters and numerous interviewees state that they survived WWII due to Aikido. Plenty of senseis have stress tested Aikido in the back alleys and bars in bad neighborhoods of Japan (Seagal, Suenaka, Saito, etc.,,).

One guy I know whose art is very similar to Aikido has been kicked out of several MMA dojos in my area. He goes there to get a good work out. He keeps breaking people. He applies an Aikido technique during the match, tells the training partner to stop for he has him, yet the MMA guys doesn't see or truly feel the problem. Not their art so they doesn't understand. They continue to fight throw the situation to their own detriment.

I was watching one episode of Lockup on TV. Saw two correction officers apply a sankyo on one hand and a nikyo on the other simultaneously on an unruly convict. That guy was hoping around and gave up really quick.